Reservac check vac part?/

Progress goes slowly on our brake project as I’ve had to order parts, wait for assistance from the beautiful Angela and figure out starting from square one what the problem is.
We had all of the cylinders re -rubbered and found one to have a major leak as the lower gasket, not the dust cover; the lower ring like gasket had a installation nick and needed to be redone. Ah, postage is getting expensive here as the cost was $10 to mail it 50 miles.

We purchased a new reservac check valve awhile back and when installing it found the old one to be in the horrible rusted out state pictured below. Tomorrow we will test drive and hopefully avoid the purchase of a new booster although I plan on that as previously discussed. This valve is junk!

I will keep the forum in the loop!

They’re not usually repairable and the replacements usually work pretty well.

Pay close attention to getting it connected the right way round. I still much that up occasionally.

I would replace all the rubber hoses as well.

Good Luck with your brakes ! I’m now having a mechanic install a new booster for me on my Mark 1 over in Salt Lake City. Apparently a simple thinf to do on a Mark 1. Hope your servo is a lot easier to install.


Yep, all new rubber hoses and got it facing forward and connected the right hose to the manifold and the other to the booster. Just put full weight on car and tightened shock tower bolts. I will check back on these VERY soon as I used nylock and not castle for the time being which has actually worked for the past 16 years. I see that the manual uses castle so that probably will be my choice soon.

I did replace the check valve as you can tell by pictures that puppy is ruined. Perhaps that was causing my no brakes/scary full on brakes syndrome??

Test drive coming up today - wish me luck!

I already had the new edition of the booster with the better pedal to braking ratio. My new one should (?) drop right in…Nothing easy on these jaguars.

I did just bleed on my right hand so the job had become satisfying. Yelling, throwing tools, blood and then beers is the only way to work on British cars!


The bride knows I’m finished working on the Mk2 when the swearing stops. Note you’ve been bleeding - I found the new seals in the master could not overcome the return spring (on the bench) - piston bottomed and stayed put. Liberal use of rubber grease fixed this problem. FWIW.

We bled all brakes to a perfect point with absolutely no air bubbles. We even had to swap out the LR brand new pipe with an old one as we were getting cold and it was rubbing on the inside of the wheel. Huge headache with the wheel coming off 4 times!

We pushed the car out of the garage with no brakes dragging. The moment we started the car, the brakes seized tight and the car would not budge.

I wish the British had put the bled nipples on the inside, as we have another problem.

The brake pedal barely moves a half inch and the car will not move. The brakes are locked fully on. I even clamped off the hose leading to the reservac and there was no difference.I did not change the rubber seals in the master.

My local guru says I should open a bled nipple to relieve pressure on the system. I will try this, but it does not seem logical. I can tell the brakes are locked on as my third brake light and the factory brake lights are constantly illuminated.

I had to leave the car outside in the cold as it is unmovable.


I woke up with another thought: We had at one point vice grip clamped off the hose from the reservoir to the master to avoid a flood of fluid pouring out of the bleeder nipples before we got that problem fixed.

Could I have crushed the hose preventing fluid from returning to the reservoir? If I change this tube will I have air in the system problems or just do it quickly to avoid problems?


The saga continues. On a whim I pushed the car this morning and she moved. I had the beautiful Angela assist me in getting it into the garage and onto the Bend Pack Ranger model. I’ll have about two feet of clearance to check I don’t know what??

I may have routed the manifold vacuum to the wrong nipple on the reservac check valve? Prolly not?? I can tell that overnight the pressure released as did the brakes locking up. All suggestions from our brake guru’s appreciated!

Remember the check valve is brand new and tested with me blowing into each end to check operations.


May I suggest a little trick I heard about on another Forum : If you can get the brakes to release … Start the car and drive it a little bit on your lane or in a parking lot and then really stomp on the brakes hard . repeat if you are not locked up. repeat again . Idea is that you may free up something inside your servo that is causing the brakes to lock on. Another method of same remedy: jack up all for wheels on stable, study jack stands and then start the car, put in gear to get the wheels turning at the rear and then aggressively put pressure on the brake pedal.

Also: do you have about 1/4" of free brake pedal push before anything happens ? Your brake return spring needs to do it’s job. Good luck !

I’m afraid to drive on the street for fear of a complete lock up and being stuck in the cu-de-sac! I can run it on the lift if you think that is safe?

The pedal moved properly on the “push, push, hold” bleeding process and then it became rock hard with barely an inch of travel even with the engine off. There is absolutely no air in the lines. All lines are new and securely tightened; pa bit more than I feel comfortable with but the dripping had to stopped.

The brake lights and third brake light are on indicating the brakes are on. Is this spring on the brake pedal? Could I manually lift the pedal to reset something?


If your stand is sturdy and the car safely raised, then I don’t see why you couldn’t start it up and engage a gear to let the rear wheels turn. once the wheels are turning, you can get into neutral and then apply the brakes agressively.
Also, you can pull the pedal back by hand and then check to see if you have any 1/4" free play in the pedal. If the pedal keeps returning then, your return spring is working.

I am not familiar with your setup, but the first thing I would try to diagnose is what happens when you disconnect the vacuum assist pipe to the servo (and block it)

The brakes should now work without atmospheric assistance, but if any problem persists it would likely be in the master or servo hydraulics,

unlikely to be calipers or hoses, as you noted your brake light illuminates which suggests the hydraulic brake pressure switch is activated

I’ll do this in the morning. Thanks


Is everything normal if you apply the brakes without the engine running?

If so it’s the servo or something associated with the servo, because everything else is always part of the braking system whereas the servo only becomes part of it when it has power from the engine.

That’s the way I’d try to narrow it down a bit.

I have a list of procedures I will test today with Angela’s help. I always need to corral the dogs first and make sure we don’t have any “accidents” in the house. I have about five tests so far I am going to handle.

Check pedal no engine.
Check pedal engine running no vacuum
Check pedal and slowly applying brakes with engine on and no vacuum.
Check pedal and slam bakes on with engine running if above step does not lock them up with no vacuum.
Hook up vacuum and test brakes with hard application which probably will lock up brakes.
I am first going to check that I hooked up vacuum lines to the correct nipples on the reservac air tank.


Good luck today ! you will probably narrow down the possible issue quite a bit.

I’m getting some good advice here. On page 332 of the SNG USA download catalog it shows the rubber hose from the manifold vacuum going to the nipple on the check valve on the reservac going to the nipple CLOSEST to the reservac. Conversely the FSM shows exactly the opposite. Either way the brakes lock when the engine is running. I will next plug that line and start the car and I guarantee you the brakes will not lock up. So that leaves either the booster or the master. Oh what fun!!

Feedback highly appreciated. It might take a peek under your cars to give me your vehicles orientation.

We are still at it and almost got the booster/servo installed yesterday. Over the years the rock shield and the booster/servo mounts have been cobbled together and are giving us an awful time.

When I was replacing the upper bump stops awhile back I inadvertently allowed the axle stud (?) the part with the 5 studs on it to fall down. Al

though easy to put in what seemed the correct spot you see by the videos that on right turns the rotor hits the shock tower. And it is VERY close in the straight ahead position which some of you noted was normal.

How would I check the upper ball joint for failure? Would I put the wheel on and look for a wobble when manually moved in and out.

I can get a video to upload of the rotor hitting tower but …